POS0261 ASSOCIATIONS BETWEEN PAIN SENSITIZATION AND PHYSICAL FUNCTION IN PEOPLE WITH HAND OSTEOARTHRITIS: RESULTS FROM THE NOR-HAND STUDY
Authors: M. Gløersen, P. Steen Pettersen, T. Neogi, J. Sexton, T. K. Kvien, H. B. Hammer, I. K. Haugen
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Pain sensitization is an important component of the pain experience in many persons with osteoarthritis (OA). Knee OA studies have suggested that pain sensitization is associated with functional limitations, but the evidence in hand OA is sparse. <h3>Objectives</h3> To assess whether pain sensitization is associated with physical function in people with hand OA. <h3>Methods</h3> We included 206 participants in cross-sectional analyses from the follow-up visit of the Nor-Hand study. Measures of pain sensitization included pressure pain thresholds (PPTs) by a handheld algometer, and temporal summation (TS) defined as increased pain during repeated stimuli. Pain and function in hands and knees/hips were self-reported on the AUSCAN and WOMAC indices, respectively. Performance-based measures of physical function included hand grip strength, the 30-second chair stand test and the 40-meter walk test (reported as walking speed). Associations between sex-standardized PPT and TS values and physical function were assessed using linear regression adjusted for potential confounders (see Table 1). The possible mediating effect of self-reported pain severity was examined with causal inference-based mediation analyses. <h3>Results</h3> The median (IQR) age was 65 (60-69) years and 86% were female. People with higher PPTs at or near the hand or knee, which may represent less peripheral and/or central sensitization, reported better function in hands and knees/hips and performed better on the performance tests than people with lower PPTs (Table 1), although not statistically significant for all outcomes. Also, a higher PPT at the trapezius muscle, representing less central sensitization, was associated with better function in the lower extremities (Table 1). No associations were found between pain sensitization and the chair stand test (data not shown), or between TS (measure of central sensitization) and hand or lower extremity function. The effects of PPTs on self-reported AUSCAN hand function appeared to be largely mediated through self-reported hand pain (e.g., indirect effect of PPT at the wrist mediated through hand pain: -1.19, 95% CI -1.95, -0.43, and direct effect: -0.20, 95% CI -0.90, 0.51). Effects of PPTs on grip strength were mediated through pain to a lesser extent (e.g., indirect effect of PPT at the wrist mediated through hand pain: 0.12, 95% CI -0.10, 0.34, and direct effect: 1.21, 95% CI 0.29, 2.13). Similarly, the mediating effects of knee/hip pain were larger in analyses of self-reported function than for performance-based measures of lower extremity function (data not shown). <h3>Conclusion</h3> Our results suggest that peripheral sensitization and possibly also central sensitization, are associated with impaired function in hands and lower extremities. For both the hand and lower extremities, measures of sensitization may have direct effects on performance-based measures of function, whereas the effect of sensitization on self-reported function appears to be mediated through self-reported pain severity. <h3>Acknowledgements</h3> The authors would like to thank the study participants, the project coordinator Heidi Gammelsrud, as well as the user representative, physicians and medical students who were involved in the Nor-Hand study. <h3>Disclosure of Interests</h3> Marthe Gløersen: None declared, Pernille Steen Pettersen: None declared, Tuhina Neogi Consultant of: Novartis, Pfizer-Lilly, Regeneron, Grant/research support from: Pfizer, Joe Sexton: None declared, Tore K. Kvien Speakers bureau: Grünenthal, Sandoz, UCB, Consultant of: AbbVie, Amgen, Celltrion, Gilead, Novartis, Pfizer, Sandoz, UCB, Grant/research support from: AbbVie, Amgen, BMS, Galapagos, Novartis, Pfizer, UCB, Hilde Berner Hammer Speakers bureau: AbbVie, UCB, Lilly, Novartis, Grant/research support from: AbbVie, Pfizer, Roche, Ida K. Haugen Consultant of: Novartis, GSK, Grant/research support from: Pfizer/Lily.